Last season was a nightmare for the Colts. Fittingly, their best victory—a Week 9 win over the eventual Super Bowl champions, the Broncos—was a Pyrrhic one. Andrew Luck threw for 252 yards and two touchdowns, but took endless body blows in the 27-24 win. Somewhere in there, his kidney was lacerated and his season soon came to an end.

Denver’s formula for reaching Luck was easy to identify. When their dynamic pass rushers weren’t straight up blowing past Indy’s sluggish blockers, the Broncos were creating opportunities through twists and stunts. These tactics are often talked about but rarely explained. On a stunt or a twist (or a “game,” because there seems to be a thousand names for the same thing across pro football), defensive lineman A attacks his blocker at an angle to create a pass rushing lane for defensive lineman B to loop into.

The Colts really had trouble in 2015 when opponents employed a third defensive lineman in this equation and stunted around two gaps, which the Broncos did with Von Miller early in Week 9.

Jonotthan Harrison, the center, failed on this play. It’s no coincidence that Colts GM Ryan Grigson used a first-round pick on Harrison’s replacement, Ryan Kelly, this offseason. The Alabama product, a stabilizing presence in Week 1 against Detroit, will be challenged to play with vision and awareness against the Broncos on Sunday. Stunts do two things to an offensive lineman. They force him to play laterally and demand that he be on the same page with the linemen next to him (emphasis: to his left and right). The blockers must pick up each other’s assignments smoothly. The better they do this, the squarer their bodies will be to the line of scrimmage (and the less laterally they’ll have to play).

Tactics like these are why we hear about the importance of having continuity along an offensive line. You can teach blockers to identify and communicate against stunts, but the nuances in execution will vary from man to man. With Ryan Kelly about to play just his second NFL game, the Broncos will test his chemistry with guards Jack Mewhort and Denzelle Good. A seventh-round rookie tackle last season, Good struggled against stunts and similar concepts in Week 1 against the Lions.

Offensive line woes aside, using stunts against the Colts works well because of Andrew Luck’s deep dropbacks. Most stunts, especially multi-gap ones, take time to unfold. The design, in theory, means the looping pass rusher reaches the quarterback at the top of his dropback. Even if the pass rush is a little late getting to Luck, it’s often effective because his courage is boundless when it comes to holding the ball. Having pass rushers loop around and in his line of vision is a smart strategy.

If last year’s game is any indication, Luck will really have to hold on to the ball in obvious passing situations. The Colts’ wideouts don’t match up well against the physicality of Denver cornerbacks Aqib Talib, Chris Harris and Bradley Roby; those three stifled the Indy in man coverage last year. (Talib took Donte Moncrief, Harris took T.Y. Hilton and Roby took whoever was rotated in at No. 3.) Rob Chudzinksi took over as Indianapolis’s offensive coordinator last year just before the Denver game. He wisely put his receivers in bunches and used switch-release concepts to make routes intersect and defenders give some cushion. Unfortunately, the execution was too erratic. It’s imperative that Indy’s receivers be sharper working together off the line on Sunday.

Chudzinski also called for runs on first and second down. The Colts didn’t post huge numbers (120 yards on 40 carries) but the commitment to a run-pass balance kept them on schedule and in fewer third-and-long situations, when stunt tactics come into play. Chudzinski also cleverly exploited Denver’s man coverage with his run designs, often sending a receiver in motion away from where the run was going and forcing the receiver’s defender away from the action.

Given how successful Denver was in using man-to-man against Carolina in the season opener, it’d be a shock if they used another scheme in Week 2. If Luck and the offensive line can survive the pass rushing stunts, they’ll have a chance to upset the Broncos again.